Method for the manufacture of a plastic component, plastic component, and shoe

ABSTRACT

Described are methods for the manufacture of a plastic component, in particular a cushioning element for sports apparel, a plastic component manufactured with such a method, for example a sole or a part of a sole for a shoe, and a shoe with such a sole. According to an aspect of the invention, a method for the manufacture of a plastic component, in particular a cushioning element for sports apparel, is provided which includes loading a mold with a first material which includes particles of an expanded material, and, during loading the mold, pre-heating the particles by supplying energy, wherein the energy is supplied in the form of at least one electromagnetic field.

CROSS REFERENCE TO RELATED APPLICATION

This application is related to and claims priority benefits from GermanPatent Application No. DE 10 2016 223 980.5, filed on Dec. 1, 2016,entitled METHOD FOR THE MANUFACTURE OF A PLASTIC COMPONENT, PLASTICCOMPONENT, AND SHOE (“the '980.5 application”). The '980.5 applicationis hereby incorporated herein in its entirety by this reference.

FIELD OF THE INVENTION

The present invention relates to a method for the manufacture of aplastic component, in particular a cushioning element for sportsapparel, a plastic component manufactured with such a method, forexample a sole or part of a sole for a shoe, as well as a shoe with sucha sole.

BACKGROUND

Nowadays, plastic components play an essential role in many areas oftechnology and everyday life. As examples, the aviation and aerospaceindustry as well as the automotive industry are mentioned. In theseareas, plastic components may, for example, serve as impact protectionelements, e.g. bumpers, or they may be used for the manufacture ofpanel-elements, seat shells, arm rests, and so forth. Plastic componentsmay also be used in the packing industry, for example, for packing upsensitive and easily damaged goods for delivery.

In all of these exemplary areas of application, it is desirable that theplastic components comprise as small a weight as possible, being,however, at the same time sufficiently resilient. In particular, withregard to plastic components being used for impact protection or forsafely wrapping up goods, plastic components should also comprise goodcushioning and absorption properties with regard to blows or hits. Inthis context, foamed plastic materials are known, like for exampleexpanded polystyrene—e.g. available from BASF under the trade names ofStyropor® or Styrodur®.

The use of expanded plastic materials has also found its way into themanufacture of cushioning elements for sports apparel, for example forthe manufacture of shoe soles for sports shoes. In particular, the useof particles of expanded thermoplastic polyurethane (eTPU), which arefused together by supplying heat in the form of steam or connected bythe use of a binder material as described in DE 10 2012 206 094 A1 andDE 10 2011 108 744 B1, was considered. The use of particles from eTPUhas turned out to be beneficial in order to provide shoe soles or partsof soles with a low weight, good temperature stability and smallhysteresis-losses with regard to the energy exerted for the deformationof the sole during running.

In addition, DE 10 2013 002 519 A1 discloses extended possibilities forthe manufacture of cushioning elements for sports apparel from suchparticles, for example by loading a mold with the particles via a streamof liquid or steam.

Common to the methods known is, however, that the processing of the basematerial to dimensionally stable components of a high quality is oftenonly possible up to a certain thickness or a certain packing density,meaning that the possible shapes of components that may be manufacturedmay be limited. This is due to the fact that the known manufacturingmethods necessitate supplying the binder material or heat energy also tothe interior of the components. For a liquid binder material or heatenergy supplied by steam, this is only possible to a limited degree forthicker components and/or may lead to imperfections, because “channels”or “inlet openings” are provided in the component to allow the binder orthe steam to homogeneously infuse the base material within the mold.Moreover, in particular when using steam as an energy carrier, it turnsout to be undesirable that a major share of the energy stored within thesteam may be lost in the mold instead of being supplied to theparticles/particle surfaces. This may, on the one hand, necessitate along preheating phase until the mold is heated up to a saturationtemperature, and may, on the other hand, delay stabilization and coolingof the fused component since the mold may have stored a large amount ofheat energy that delays cooling. Therefore, the method may be protractedand very energy inefficient.

It is therefore an objective underlying the present invention to provideimproved methods for the manufacture of plastic components, inparticular of cushioning elements for sports apparel, which allow themanufacture of complexly shaped plastic components with potentiallygreater thickness and packing densities, without significantlycompromising the quality of the finished components. Furthermore, themanufacturing effort shall be kept low and the manufacturing and coolingduration short, and the method shall further be as energy efficient aspossible while making do without poisonous or environmentally hazardoussubstances.

SUMMARY

The terms “invention,” “the invention,” “this invention” and “thepresent invention” used in this patent are intended to refer broadly toall of the subject matter of this patent and the patent claims below.Statements containing these terms should be understood not to limit thesubject matter described herein or to limit the meaning or scope of thepatent claims below. Embodiments of the invention covered by this patentare defined by the claims below, not this summary. This summary is ahigh-level overview of various embodiments of the invention andintroduces some of the concepts that are further described in theDetailed Description section below. This summary is not intended toidentify key or essential features of the claimed subject matter, nor isit intended to be used in isolation to determine the scope of theclaimed subject matter. The subject matter should be understood byreference to appropriate portions of the entire specification of thispatent, any or all drawings and each claim.

According to certain embodiments of the present invention, a method formanufacturing a plastic component, in particular a cushioning elementfor sports apparel, comprising: loading a mold with a first material,which comprises a particles of an expanded material; and while loadingthe mold, pre-heating the particles by supplying energy, wherein theenergy is supplied in a form of at least one electromagnetic field.

In certain embodiments, the loading step comprises transporting theparticles from a container to the mold via at least one feed line.

In some embodiments, the particles are pre-heated while in at least oneof the container and the at least one feed line.

The particles, in certain embodiments, are pre-heated in the mold priorto closing the mold.

The energy, in some embodiments, supplied by the at least oneelectromagnetic field is varied over time.

In certain embodiments, the energy supplied by the at least oneelectromagnetic field is gradually increased over time.

In some embodiments, the method further comprising a step of fusingsurfaces of the particles by supplying energy in a form of at least oneelectromagnetic field.

The form of the at least one electromagnetic field used for pre-heatingthe particles, in certain embodiments, is different than the form of theat least one electromagnetic field used for fusing the surfaces of theparticles.

The particles, in some embodiments, comprise at least one of: expandedthermoplastic polyurethane, eTPU; expanded polyamide, ePA; expandedpolyetherblockamide, ePEBA; polylactide, PLA; polyether-block-amide,PEBA; polyethylene terephthalate, PET; polybutylene terephthalate, PBT;and thermoplastic polyester ether elastomer, TPEE.

In certain embodiments, the particles further comprise an energyabsorbing material, which absorbs the energy supplied by the at leastone electromagnetic field such that the energy absorbing materialcontributes to the step of fusing the surfaces of the particles.

In some embodiments, the particles are mixed with the energy absorbingmaterial prior to the loading step.

The energy absorbing material, in certain embodiments, comprises atleast one of water and a metal.

The energy, in some embodiments, is supplied in a form of radiation in amicrowave range, 300 MHz-300 GHz.

In certain embodiments, the energy is supplied by electromagneticinduction.

In some embodiments, more energy is supplied to the particles in a firstpartial region of the mold than in a second partial region of the mold.

The energy, in certain embodiments, is supplied to the particles in afirst partial region of the mold with an electromagnetic field with afirst frequency and in a second partial region of the mold with anelectromagnetic field with a second frequency, wherein the secondfrequency is different from the first frequency.

An average amount of the energy absorbing material per particle, in someembodiments, varies within the mold.

In certain embodiments, the mold is further loaded with a secondmaterial, which remains substantially unaltered by the at least oneelectromagnetic field.

In some embodiments, a ratio of an amount of energy absorbed by thefirst material to a total amount of energy absorbed by the firstmaterial and the mold lies in a range 1.0-0.2.

According to certain embodiments of the present invention, a method formanufacturing a cushioning element for sports apparel, comprising:opening a mold by a predetermined amount into a loading position,wherein the mold comprises at least two mold parts and the predeterminedamount by which the mold is opened influences an available loadingvolume of the mold; loading a first material which comprises particlesof an expanded material into the loading volume created by opening themold; closing the mold into a closed position; and fusing surfaces ofthe particles by at least supplying energy in a form of at least oneelectromagnetic field.

In certain embodiments, in the loading position of the mold, the atleast two mold parts are in different areas of the mold spaced apart atvarying distances compared to the closed position of the mold, so thatduring the step of closing the mold, the at least two mold parts aremoved together over different distances in the different areas.

In some embodiments, at least one of the at least two mold partscomprises several individual sub-parts, and wherein a distance betweenthe at least two mold parts in the loading position of the mold may beindividually controlled for each sub-part in order to obtain the varyingdistances in the different areas.

In certain embodiments, during the step of closing the mold, at leastone of the at least two mold parts is pivoted around an eccentricallyarranged swivel axis.

In some embodiments, during the step of closing the mold, the particlesare differently compressed in the different areas of the mold.

The predetermined amount by which the mold is opened, in certainembodiments, influences mechanical properties of the cushioning element.

The cushioning element, In some embodiments, is a shoe sole or part of ashoe sole.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed description, embodiments of the invention aredescribed referring to the following figures:

FIGS. 1a-i are diagrams illustrating an inventive manufacturing methodaccording to certain embodiments of the present invention.

FIGS. 2a-c are perspective views of plastic components manufacturedaccording to an exemplary manufacturing method according to certainembodiments of the present invention.

FIG. 3 is a perspective view of an apparatus for the manufacture ofparticle foam components according to certain embodiments of the presentinvention.

BRIEF DESCRIPTION

This objective is at least partially solved by aspects of the presentinvention.

According to an aspect of the present invention, a method for themanufacture of a plastic component, in particular a cushioning elementfor sports apparel, is provided which comprises loading a mold with afirst material which comprises particles of an expanded material, and,during loading the mold, pre-heating the particles by supplying energy.The energy is supplied in the form of at least one electromagneticfield.

Particles of an expanded material will sometimes also be called “foamparticles” in this document, and the manufactured plastic componentswill consequently sometimes be called “particle foam components”. Otherterms by which such particles of an expanded material may be referred toinclude “beads” or “pellets”, for example.

By pre-heating the particles already during the loading of the mold, theamount of energy that must be supplied to the particles within the moldmay be reduced. This may help reduce the molding time, save energy, forexample, by avoiding excessive energy absorption by the mold, and alsofacilitate cooling and stabilization of the molded component. Theseeffects may further be promoted by the fact that the energy is providedby at least one electromagnetic field, i.e. the energy provision is notcoupled to any kind of material transport, like injection of energeticsteam, for example. Pre-heating the particles already during loading ofthe mold can also contribute to allowing a more fine-tuned control ofthe manufacturing method in general, as different subsets of theparticles used for the manufacture of a given component may bepre-heated to different degrees, for example.

The loading may comprise the transport of the particles from a containerto the mold via at least one feed line.

This can facilitate automatization of the manufacturing method, forexample, in an automated production line.

The particles may be pre-heated while in the container and/or in thefeed line.

Pre-heating the particles in the container may be beneficial since itmay only require little effort. On the other hand, pre-heating theparticles in the feed line may be beneficial, for example, compared topre-heating the particles in the container, as it might help avoid thatthe pre-heating has already subsided by the time the particles reach themold. In some embodiments, a combination of both options is used. Forexample, in the container the particles may be provided with a certainamount of “basic” pre-heating, while in the feed line a precise desiredamount of pre-heating may be imparted to the particles.

The particles may also be pre-heated in the mold prior to closing themold.

Pre-heating the particles directly in the mold, prior to closing themold, may be desirable, for example, if very precise control of theamount of pre-heating is desirable, since the time between imparting thepre-heating and the actual molding of the component may be minimized.

In some embodiments, the energy supplied by the at least oneelectro-magnetic field is varied over time.

The energy supplied by the at least one electromagnetic field may begradually increased over time.

Benefits of these options will be discussed in the detailed descriptionfarther below.

The method may further comprise the step of fusing the surfaces of theparticles by supplying energy, wherein the energy may again be suppliedin the form of at least one electromagnetic field.

The type/nature of the electromagnetic field used for the pre-heatingmay be different to the type/nature of the electromagnetic field usedfor fusing the surfaces of the particles.

However, in some embodiments, the type/nature of the electromagneticfield used for the pre-heating is the same as the type/nature of theelectromagnetic field used for fusing the surfaces of the particles.

This may simplify the constructional setup used for the manufacture, forexample, due to only one source of electromagnetic field beingnecessary.

The use of at least one electromagnetic fields for supplying energy tothe particles for fusing the surfaces of the particles may allow themanufacture of plastic components with various thicknesses and complexgeometry, too, since supplying the energy is not coupled to any kind ofmaterial transport, as for example the introduction of a binder orsteam. The at least one electromagnetic field may be chosen such that itpermeates the mold loaded with the particles essentially homogeneouslyand supplies an essentially constant amount of energy to all particles,such that a homogeneous and constant fusing of the particle surfaces isachieved throughout the entire plastic component and in every depth ofthe component. Or, the at least one electromagnetic field is chosen suchthat the supply of energy to the particles arranged within the moldchanges locally, as described in more detail in the following. In thisway, the nature and degree of the fusing of the particle surfaces may beinfluenced locally. In particular, the fusing of the particle surfaceswithin the interior of the plastic component may be controlledindependently of the fusing of the particle surfaces at the surface ofthe plastic component.

In conjunction with the pre-heating of the particles as describedherein, a very detailed control of the manufacturing method may bepossible, such that the properties and characteristics of themanufactured components may be adjusted and tuned very precisely.

In the following, some exemplary ways of controlling the manufacturingprocess are provided and it is described how different manufacturingparameters may have an influence on the properties of the manufacturedcomponents and/or the manufacturing method itself, for example itsduration or energy consumption. As the skilled person will understand,these options may also be combined with one another.

For example, the density of the particles in the molding cavity caninfluence the energy absorption of the particles and, thus, the energyabsorption of the part. Increasing the density of the particles can leadto improved heating. The improved heating is due to air having a lowdielectric loss factor. Therefore, minimizing the air involved in thefusing process increases the absorption of the energy provided by theelectromagnetic field, thus, improving the fusion of the particles.

For the same reasons, a mold with a higher compression ratio of theparticles or a larger crack gap will also result in better energyabsorption due to the increased packing density of the particles. It ispointed out that this is particularly beneficial over the known steamchest molding where it is known that an increased packing densityincreases cycle time due to the increased difficulty of heating theparticle surfaces.

It is explicitly mentioned at this point that for clarity reasons, everykind of energy supply is linguistically associated with its ownelectromagnetic field within this application. When talking about “atleast one electromagnetic field”, this can therefore mean that at leastone energy source is present which supplies the energy for thepre-heating and/or fusing in the form of “its electromagnetic field”. Insome embodiments multiple energy sources are used or one energy sourcemay emit radiation with different frequencies and so forth, such that inthese cases multiple electromagnetic fields are (linguistically) madereference to. These fields superimpose at a given point in space to formthe physical electromagnetic field at this point in space.

The particles may be randomly arranged. However, the particles or atleast some of the particles may also be aligned to each other or beotherwise intentionally arranged within the mold.

The particles may, for example, comprise at least one of the followingmaterials: expanded thermoplastic polyurethane (eTPU), expandedpolyamide (ePA), expanded polyether-block-amide (ePEBA), polylactide(PLA), polyether-block-amide (PEBA), polyethylene terephthalate (PET),polybutylene terephthalate (PBT) and thermoplastic polyester etherelastomer (TPEE).

Other possible polymers used for making the expanded particles may beselected from at least one of polyamides, polyester, polyetherketones,and polyolefins. The polyamide may be at least one of homopolyamide,copolyamide, polyetherblockamide, and polyphthalamide. Thepolyetherketone may be at least one of polyether ketone (PEK), polyetherether ketone (PEEK), and polyetherketoneketone (PEKK). The polyolefinmay be at least one of polypropylene (PP), polyethylene (PE), olefinco-block polymer (OBC), polyolefine elastomer (POE), polyethyleneco-vinyl acetate (EVA), polybutene (PB), and polyisobutylene (PIB). Theexpanded polymer material may include a suitable chain extender.

Moreover, the polymer may be selected from at least one ofpolyoxymethylene (POM), polyvinylidene chloride (PVCD), polyvinylalcohol(PVAL), polylactide (PLA), polytetrafluoroethylene (PTFE),polyvinylidene fluoride (PVDF), tetrafluoroethylene (FEP),ethylene-tetrafluoroethylene (ETFE), polyvinylfluoride (PVF),perfluoroalkoxy (PFA), and thermoplastic polyurethanes (TPU). In anexample, the polymer comprises polybutylene terephthalate (PBT) and thechain extender comprises at least one selected from a polymeric materialcontaining epoxy groups, pyromellitic dianhydride, styrene maleicanhydride, or combinations of at least one thereof, in particular astyrene-acrylate copolymer containing reactive epoxy groups.

Further, the polymer may comprise polyamide (PA) orpolyether-block-amide (PEBA) and the chain extender may then comprise atleast one selected from a polymeric material containing epoxy groups,pyromellitic dianhydride, styrene maleic anhydride, or combinations ofat least one thereof, in particular a styrene-acrylate copolymercontaining reactive epoxy groups. Also, the polymer may comprisethermoplastic polyester ether elastomer (TPEE) and the chain extendermay then comprise at least one selected from a polymeric materialcontaining epoxy groups, pyromellitic dianhydride, styrene maleicanhydride, or combinations of at least one thereof, in particular astyrene-acrylate copolymer containing reactive epoxy groups.

Generally, any polymer materials, e.g. semi-crystalline polymers, whichabsorb electromagnetic (RF) radiation to a sufficient degree, i.e. havea relatively high dielectric loss factor, may be used, such that noadditional heat transfer medium is needed. Still, for some materialssuch as ePP (expandable polypropylene) or ePS (expandable polystyrene),an additional heat transfer medium may be necessary. Moreover, at leastone additive may be incorporated into the polymer material to increasethe dielectric loss factor.

Plastic components comprising particles from at least one of thematerials mentioned above distinguish themselves by having very goodcushioning properties and a good elasticity and energy return, and theymay at the same time be very lightweight. Their properties may also betemperature independent to a large extent. It may therefore bebeneficial to use mixtures (or regions) of different expanded particlesin the mold, which may then be formed into a component using the methodsdescribed herein.

In other embodiments, the particles comprise an energy absorbingmaterial which absorbs the energy supplied by the at least oneelectromagnetic field, such that the energy absorbing materialcontributes to the pre-heating of the particles and/or the fusing of thesurfaces of the particles.

The energy absorbing material can serve the purpose of increasing theamount of energy absorbed by the particles from the electromagneticfields per time unit. This may accelerate the manufacture of thatplastic component and make it more energy efficient. An energy absorbingmaterial may also be used to locally influence the amount of absorbedenergy and hence the degree to which the particles are pre-heated and/orthe particle surfaces are fused together, as discussed in further detailbelow.

In the case where it is only dispensed on the surfaces of the particles,the use of an energy absorbing material can further have the benefitthat the particles are pre-heated and/or fused together only at theirsurfaces, while the electromagnetic field permeates the interior of theparticles without noticeably depositing energy there, such that the cellstructure and hence the elastic properties of the particles may remainessentially unaltered in their interior.

“Essentially unaltered” in this respect may, for example, mean thatthere are no noticeable differences in the physical properties relevantfor the intended use of the component before and after supplying theenergy.

The particles may be provided with the energy absorbing material priorto the loading of the mold.

Prior to being loaded into the mold, the particles may, for example, bestored in the energy absorbing material in a storage container and/or beintermixed, coated, soaked or impregnated with the energy absorbingmaterial, and so forth. The energy absorbing material may be added tothe particles in a feed line which is used for loading the mold with theparticles. This may allow a dosed addition of the energy absorbingmaterial such that the amount of energy absorbing material per particlemay be adjusted and varied during the loading of the mold.

The energy absorbing material may, for example, comprise water.

Water is particularly cheap, environmentally friendly and easily handledand it has the further benefit that it does not enter into anundesirable chemical reaction with the particles which may, for example,influence the surface or cell structure or the appearance of theparticles in an unwanted manner.

In some embodiments, the energy absorbing material comprises a metal.

Metal, for example in the form of a metal powder, may be beneficial asit may absorb a particularly high amount of energy from the at least oneelectromagnetic field while at the same time being easily handled anddosed. A metal may, moreover, also serve the purpose of influencing theappearance of the plastic component, if desirable, for example toprovide the plastic component with a metallic shininess.

The energy may, for example, be supplied in the form of radiation in themicrowave range, i.e. with a frequency in the range from 300 MHz-300GHz.

Microwave generators are commercially available and may be implementedinto a manufacturing device for performing an inventive method withcomparatively little effort. In addition, in some embodiments, themicrowave radiation is focused essentially onto the cavity of the moldin which the particles of the expanded material are loaded or onto afeed line or storage container by a suitable device, such that theenergy efficiency of the method is increased. Furthermore, the intensityand frequency of the microwave radiation may be easily changed andadapted to the respective requirements.

The energy may also be supplied in the form of radiation in theradiofrequency range, i.e. with a frequency in the range from 30 kHz-300MHz.

Radiofrequency generators are also commercially available and may beeasily implemented in a manufacturing device. Moreover, radiofrequencyradiation may be focused on the respective parts of the manufacturingdevice, and its intensity and frequency may be adapted to therequirements.

In other embodiments, the energy is supplied in the form of radiation ina frequency range different from the frequency ranges mentioned above.

As a specific example, the energy may be supplied in the form ofinfrared (IR) radiation. The use of ultraviolet (UV) radiation may alsobe considered.

In some embodiments, the energy is supplied by electromagneticinduction.

Electromagnetic induction describes the creation of an electric field bya temporal variation of the magnetic flux. Hence, also in the case ofelectromagnetic induction, energy is supplied in the form of atemporally varying electromagnetic field. Electromagnetic induction mayin particular be used to pre-heat the particles and/or fuse the particlesurfaces, if the particles or their surfaces comprise a material or arecoated with a material which comprises a certain electric conductivity.Then, the electric field created by the electromagnetic induction cancreate currents in this material, which heat up the particles orparticle surfaces. This may allow the selective and locally focusedsupply of energy. Hence, the degree of pre-heating of the particlesand/or fusing of the particles at their surfaces may be influenced andcontrolled very precisely, also for particles arranged within theinterior of the plastic component.

Whether the use of radiation in the microwave range, radiation in theradiofrequency range, or electromagnetic induction is more desirablemay, for example, depend on the question from which material the mold ismade. In some embodiments, one chooses the option in which the moldabsorbs the smallest possible amount of energy from the usedelectromagnetic field(s). In other embodiments, combinations of theabove mentioned options are used.

In any of the above cases, i.e., supplying energy via radiation orelectromagnetic induction, the component essentially contains noadditional water, compared with steam chest molding. This allows themanufactured components to be passed on to further processing stepsstraightaway. For example, the further manufacturing steps of assembly(e.g., of a sole or sports apparel in general) and/or attaching to anupper can directly follow the manufacture of the component (for example,the further manufacturing steps may involve infrared welding and/or RFfusing).

The process of manufacture as described herein is therefore desirablefor manufacturing customized sports apparel such as shoes. Inparticular, the sports apparel may be manufactured in a store using asuitable method for manufacture as described herein. The process ofcustomized manufacture of sports apparel is described in further detailin the European patent applications EP 2 862 467 A1 and EP 2 865 289 A1of Applicant.

In other embodiments, more energy is supplied to the particles in afirst partial region of the mold than to particles in a second partialregion of the mold. This may apply both to the pre-heating of theparticles within the mold prior to closing the mold as well as to thefusing of the particle surfaces.

In this way, different partial regions may be created within the plasticcomponent, which differ in their respective thickness, stiffness,breathability, flexibility, elasticity, feel, appearance or with regardto other characteristics, wherein potentially the same base material maybe used, which might facilitate the manufacture.

In this document, the amount of energy which is supplied to theparticles, in some embodiments, designates the amount of energy that isactually absorbed by the particles from the electromagnetic field(s).

In some embodiments, energy is supplied to the particles in a firstpartial region of the mold with an electromagnetic field with a firstfrequency and in a second partial region of the mold with anelectromagnetic field with a second frequency, wherein the secondfrequency differs from the first frequency.

Energy may, for example, be supplied to the particles in the firstpartial region of the mold with electromagnetic radiation with a higherfrequency than in the second partial region of the mold. Herein, bothkinds of radiation with their differing frequencies may, for example,originate from a single radiation source, or separate radiation sourcesmay be used that each emit radiation with one of the two frequencies. Inother embodiments, a generalization to multiple kinds of radiation withmore than two different frequencies is used.

In some embodiments, the intensity of the radiation (or of the differentkinds of radiation) varies locally in different regions of the mold and,in this way, the degree of the pre-heating and/or fusing of the particlesurfaces may be influenced.

On the other hand, to enable consistent energy application to parts withvarying component thickness, (in shoe manufacture of midsoles, varyingcomponent thickness is sometimes referred to as wall thickness), thetool thickness may be varied. For example, higher density material mayheat quicker, and, therefore, the tool may be locally adjusted to absorbmore energy to balance with the energy absorption of the lower densityareas. This may be beneficial because it is easier to apply a constantelectromagnetic field than to apply a varying electromagnetic field.Thus, by varying the density of the material, the properties of thecomponent may be influenced in a simpler way than by applying varyingelectromagnetic fields (e.g., varying in frequency).

In other embodiments, the average amount of energy absorbing materialper particle varies within the mold.

This provides an embodiment which is complementary to the abovementioned options of changing the properties of the electromagneticfield(s) to locally influence the amount of energy which is supplied tothe particles (i.e. the amount of energy which is actually absorbed bythe particles). In some embodiments, prior to loading the mold, acertain amount of particles is pre-mixed with different amounts ofenergy absorbing material and the different mixtures are then positionedin different partial regions of the mold according to the desired degreeof pre-heating and/or fusing. Or, the energy absorbing material may beadded to the particles in a dosed manner during the loading of the mold,for example in a feed line, such that the content of energy absorbingmaterial of the particles loaded into the mold may be varied.

The mold may further be loaded with a second material which remainsessentially unaltered by the at least one electromagnetic field.

This may, for example, be a material the electromagnetic field permeateswithout being absorbed by the material to a noticeable degree. Inparticular, the second material may be free from energy absorbingmaterial. “Essentially unaltered” may mean that the second material doesnot melt or start melting or become softer or harder. Furtherexplanations with regard to the meaning of the term “essentiallyunaltered” were already put forth above and these explanations alsoapply here.

The second material may, for example, also comprise particles of anexpanded material, in particular particles of eTPU, ePA, ePEBA, PLA,PEBA, PET, PBT and/or TPEE. Other examples have been described above.

Hence, an inventive manufacturing method may allow manufacturing aplastic component from a single base material which comprises partialregions that are e.g. strongly fused and/or stiffer and/or impermeableto air, as well as partial regions comprising a loose assemblage of theparticles such that the plastic component may comprise a lower stiffnessbut higher breathability in these regions, and so forth.

The manufacturing method may also involve a step of stabilizing theparticle foam component after fusing. This may be done by keeping thecomponent in the tool after fusing so that the component maintains thedesired part shape. The greater the volume of material in the mold themore beneficial it is to stabilize the component. The stabilization stepmay also include, for example, cooling channels or cooling ribs, topermit control of the rate at which the component cools and, thus, isstabilized.

The manufacturing method may also involve the additional step of using afoil to form a skin on the particle foam. The foil may be fused with theexternal foam particles. In some examples, this may be TPU, but othermaterials that exhibit a high degree of polarity for bonding may beused, such as PVC, which is the most sensitive in terms of polarity.

The particles of the second material may be randomly arranged. Or, theparticles or at least some of the particles of the second material maybe aligned to each other or be otherwise intentionally arranged withinthe mold.

A ratio of the amount of energy absorbed by the first material to thetotal amount of energy absorbed by the first material and the mold maylie in the range 1.0-0.2, or it may lie in the range 1.0-0.5, or it mayeven lie in the range 1.0-0.8.

In case a second material (and potentially even further materials) isloaded into the mold, the above ranges may apply to the ratio of theamount of energy absorbed by the first material to the total amount ofenergy absorbed by all materials within the mold plus the energyabsorbed by the mold.

As already mentioned numerous times, the inventive manufacturing methodmay allow selectively supplying energy to regions where it is needed forthe pre-heating of the particles and/or the fusing of the particlesurfaces. It may, in particular with regard to the fusing of theparticle surfaces in the closed mold, be possible by a suitable choiceof the materials used for the mold to have the mold absorb only aninsignificant amount of energy from the electromagnetic field. For onething, this makes the manufacturing method more energy efficient. It mayalso help to prevent the mold from heating up noticeably, which in turnmay shorten the cooling process significantly. A preheating of the moldmay also be avoided. The above mentioned ratios of the amount of energywhich is absorbed by the first material with the particles to the totalamount of energy which is absorbed by all materials in the mold plus themold itself have turned out to be realistic.

However, a method for the manufacture of sporting goods may also involvea step of heating or preheating at least part of the walls of the mold.This may also contribute to the pre-heating of the particles themselves.In this way, the surface quality may be improved and a better packing ofthe particles up to the mold surface may be achieved. In someembodiments, this may be achieved by applying a material to the moldsurfaces that has a higher dielectric loss than material of the moldsurface and so absorbs some radiation and thus heats up, without meltingthe material. Another method of achieving this manufacturing step couldalso be using a tool (e.g., a laser sintered tool which allows for morecomplex channels and also channels closer to the mold surface) to allowheating of the mold through passing a fluid around/through the tool. Thefluid should have a low dielectric loss factor. In general, heatingabove the melting temperature of the components would lead to thecomponent walls being melted, which is not desirable. It should be notedthat care should be taken when heating the mold to a temperature nearto, at, or above the glass transition temperature of the materials asthe dielectric absorption of materials changes drastically in polymersabove this value, i.e. increased absorption would mean that heatingwould rapidly ramp up over this temperature. Therefore, in some cases,heating the mold to a temperature near to, at, or above the glasstransition temperature of the material should be avoided.

It is also mentioned that a laser sintered tool with complex channelsand/or channels close to the mold surface may also be beneficial in thatthe channels can allow rapid cooling of the tool by passing a coolingfluid through the channels. The tool may also comprise cooling ribs tofacilitate cooling.

Any mold manufacturing method known in the art may be used to constructa mold for use in the methods described herein.

For example, a mold may comprise an epoxy resin, in whole or in part.Other mold materials can also be used in connection with themanufacturing method. For example, the manufacturing method may involvethe step of providing a mold of PTFE, PE, PEEK, UHMWPE(Ultra-high-molecular-weight polyethylene), or other materials which arestructurally stable during electromagnetic field application. Providingsuch structurally stable materials can improve the step of fusing thesurfaces of particles.

The use of an epoxy resin may also facilitate the manufacture of moldswith complex three-dimensional geometry. Furthermore, an epoxy resin maybe electrically non-conductive, such that, for example, a heating up ofthe mold or parts of a mold may be avoided or decreased. A mold or partof a mold made from epoxy resin may be basically non-absorbing forelectromagnetic radiation, too. However, as discussed above, in somesituations an additional step of heating at least part of the mold maybe beneficial.

A further aspect of the present invention is provided by a method forthe manufacture of a cushioning element for sports apparel whichcomprises: (a) opening a mold by a predetermined amount into a loadingposition, wherein (b) the mold comprises at least two mold parts, andthe amount by which the mold is opened in step (a) influences anavailable loading volume of the mold; (c) loading a first material whichcomprises particles of an expanded material into the loading volumecreated by opening the mold in step (a); (d) closing the mold into aclosed position; and (e) fusing the surfaces of the particles by atleast supplying energy in the form of at least one electromagneticfield.

The mold may comprise two parts, but it may also comprise more than twoparts. Having more than two parts may, for example, facilitate loadingof the mold or demolding of the finished component.

For example, in the case of a mold with two mold parts, the two moldparts may provide a gap or crack between them in the loading position ofthe mold. The loading position of the mold may therefore also bereferred to as the “crack-gap position” of the mold (irrespective of thenumber of mold parts). Through this crack, the first material may beloaded into the loading volume created between the mold parts by openingthe mold.

The available loading volume may be completely filled with the firstmaterial. In other embodiments, the available loading volume is notcompletely filled with the first material, either to be then filled upby further materials, or to simply be partially left void. The loadingmay be performed without additional pressure (e.g., under atmosphericpressure), or the first material may be loaded into the mold underpressure (e.g., above atmospheric pressure). The loading may befacilitated by the use of a stream of air or liquid, for example.

The loading of the mold through a gap or crack between individual moldparts may be referred to as “crack-gap loading”. The present aspect ofthe invention may therefore also be referred to as the “crack-gapmethod.”

As mentioned, the predetermined amount by which the mold is opened inthe loading position in step (a), and hence the crack height, influencesthe available loading volume into which the first material (andpotentially further materials) may be loaded in step (c). A furtherfactor that influences the available loading volume is, of course, thegeneral size of the mold, i.e. the size of the component that ismanufactured (e.g., a shoe size if the method is used to manufacture ashoe sole or part of a shoe sole). The available loading volume, inturn, can have an influence on the amount of compression the firstmaterial and, in particular, the particles of the expanded materialexperience upon closing of the mold during step (d) (assuming, forexample, that the available loading volume is completely filled with thefirst material and that the closed position of the mold is always thesame; otherwise, the filling height and specific configuration of theclosed position may also influence the amount of compression).

The energy for fusing the surfaces of the particles may be supplied inthe form of at least one electromagnetic field. However, other forms ofsupplying energy, for example using (pressurized) steam, may alsocontribute to the fusion of the surfaces of the particles. It ismentioned that the details and features of electromagnetic fields usedto supply energy described throughout this specification may also applyto the present aspect of the invention, even if these details andfeatures are described in the context of a different aspect. They aretherefore not repeated here for conciseness.

In the loading- (or crack-gap-) position of the mold, the mold partsmay, in different areas of the mold, be spaced apart at varyingdistances compared to the closed position of the mold, such that duringstep (d) of closing the mold the mold parts are moved together overdifferent distances in the different areas.

At least one of the mold parts may, for example, comprise severalindividual sub-parts, and the distance between the mold parts in theloading position of the mold may be individually controlled for eachsub-part, in order to obtain the varying distances between the moldparts in the different areas of the mold.

In other embodiments, during step (d) of closing of the mold, at leastone of the mold parts is pivoted around an eccentrically arranged swivelaxis.

During step (d) of closing the mold, the particles may be differentlycompressed in different areas of the mold. For example, a mold part withindividual sub-parts, or a mold part being pivoted around aneccentrically arranged swivel axis may, upon closing of the mold, leadto different degrees of compression in different areas of the mold.

The predetermined amount by which the mold is opened in step (a) mayinfluence the mechanical properties of the cushioning element. Suchmechanical properties may, for example, include the stiffness, densityand/or elasticity of the cushioning element. For example, a larger crackheight may lead to a larger available loading volume, to more materialbeing loaded into the mold, and hence to a stronger compression of theloaded material upon closing of the mold. This may lead to a higherdensity and higher stiffness of the manufactured cushioning element, forexample.

Other factors that might influence the mechanical properties include,for example, the material composition of the first material being loadedinto the mold, the loading pressure (e.g., atmospheric or above), theamount and kind of energy supplied for fusion of the particle surface,the duration of fusion, and so forth.

The cushioning element manufactured in this way may, for example, be ashoe sole or part of a shoe sole, for example a midsole.

Further details, options and benefits of this “crack-gap method” will bementioned in the detailed description further below.

It is also emphasized that the “crack-gap method” for the manufacture ofa cushioning element may be combined with the other aspects of thepresent invention described above and further below, but the differentaspects of the present invention may also be practiced individually.

A further aspect of the present invention is provided by a plasticcomponent, in particular a cushioning element for sports apparel (e.g.,a shoe sole or part of a shoe sole), manufactured with embodiments ofthe inventive method.

A further aspect of the invention relates to a shoe, in particular asports shoe, with such a cushioning element. The shoe may be a runningshoe.

By use of the inventive manufacturing method for the manufacture of sucha plastic component, the properties of the manufactured plasticcomponent may be selectively and locally influenced withoutnecessitating a complicated set up of the manufacturing device.Moreover, the manufacture may be energy efficient and environmentallyfriendly and may be completed in comparatively little time. Hence, theinventive manufacturing method may be suitable for use in massproduction, for example the manufacture of shoes with soles or parts ofsoles manufactured by use of the inventive method. Moreover, the methodmay be automated to a large degree and different kinds of plasticcomponents may be manufactured with a single manufacturing device, forexample by adapting the frequency, intensity, duration of radiation,focusing, and other properties of the electromagnetic field(s) to therespective requirements for each plastic component.

DETAILED DESCRIPTION

The subject matter of embodiments of the present invention is describedhere with specificity to meet statutory requirements, but thisdescription is not necessarily intended to limit the scope of theclaims. The claimed subject matter may be embodied in other ways, mayinclude different elements or steps, and may be used in conjunction withother existing or future technologies. This description should not beinterpreted as implying any particular order or arrangement among orbetween various steps or elements except when the order of individualsteps or arrangement of elements is explicitly described.

Some embodiments of an inventive method are described in the followingdetailed description primarily with respect to cushioning elements forsports apparel, in particular soles for shoes. It is, however,emphasized that the present invention is not limited to theseembodiments. To the contrary, it may also be used for plastic componentsfor the automotive industry, for example for the manufacture of bumpers,fenders, panel-elements, seat shells or arm rests, for plasticcomponents for the aviation and aerospace industry, for plasticcomponents for the packing industry, for plastic components for sportsequipment, and so forth.

Reference is further made to the fact that in the following onlyembodiments of the invention may be described in more detail. Theskilled person will understand, however, that the optional method stepsand modifications described with reference to these specific embodimentsmay also be modified or combined with one another in a different mannerwithin the scope of the invention, and that individual steps or optionalfeatures of the method may also be omitted, if these seem dispensable.In order to avoid redundancies, reference is therefore made to theexplanations in the preceding sections, which also apply to thefollowing detailed description.

FIGS. 1a-i illustrate embodiments of an inventive method 100 for themanufacture of a plastic component. These are schematic representations,such that the proportions shown in FIGS. 1a-i need not necessarily matchthe actual proportions in a real-life application of the method 100.Rather, FIGS. 1a-i serve the purpose of indicating to the skilled personthe scope of the present invention including potential design optionsand modifications of the method 100, as well as the different option toadapt the method 100 according to a given set of requirements.

The method 100 comprises the step of loading a mold 110 with a firstmaterial comprising particles 120 of an expanded material, also called“foam particles” herein, as shown in FIG. 1 a.

During loading of the mold 110, the method 100 may also comprise thestep of pre-heating the particles 120 by supplying energy, wherein theenergy is supplied in the form of at least one electromagnetic field130, 135, 140 (for more details on these fields, see below).

Options and features pertaining to the pre-heating step have alreadybeen discussed in detail above and are therefore not all repeated here,for conciseness. Some further details and benefits will be describedfarther below. It is also mentioned that, whenever the energy-absorbingcharacteristics of the particles 120 are discussed in the context of thefusion of the particle surfaces in the following, the sameconsiderations may also apply to the pre-heating of the particles 120,where physically possible.

Importantly, however, it is emphasized that the manufacture of acomponent as described in the following may, in principle, also beperformed without the pre-heating step. That is, the features anddetails described in the following with regard to the mold 110 or thefusion of the particle surface, for example, are to be regarded asindependent aspects that may be practiced without pre-heating theparticles 120, although certain synergetic benefits (e.g., reduced cycletimes, to name only one) may be achieved by combining these aspects witha pre-heating of the particles 120.

The mold 110 may, for example, comprise two or more mold parts 112, 113which may be movable relative to one another. The mold 110 encompasses acavity 115 having a shape corresponding to the plastic component that isto be manufactured.

The mold 110 or the mold parts 112, 113 may, for example, comprise anepoxy resin. The use of epoxy resin for the manufacture of the mold 110or the mold parts 112, 113 may allow providing molds 110 comprising acavity 115 with a very complex three-dimensional geometry. Hence,complexly shaped plastic components may be manufactured with theinventive manufacturing method 100. However, other mold materials canalso be used in connection with the method 100. For example, the method100 may involve the step of providing a mold 110 of PTFE, PE, PEEK, orother materials which are structurally stable during electromagneticfield application.

The surface material of the mold 110 or the mold parts 112, 113 may beselected so that it has a similar loss factor to that of the foamparticles 120 (i.e. the particles 120 of expanded material). One exampleof such suitable material is epoxy resin. Providing the surface of themold 110 or mold parts 112, 113 with a material with a loss factorsimilar to that of the particles 120 can lead to a substantially uniformheating of both the particles 120 and the walls of the mold 110enclosing the molding cavity 115, so that a better surface fusion of thecomponent may be obtained. The surface of the mold 110 may, for example,be altered by a coating process or by applying a suitable surfacematerial in another way known in the art.

Also, the mold parts 112, 113 may comprise capacitor plates (not shown).The capacitor plates may be arranged on an inner side of the mold parts112, 113 (i.e. on the side of the parts 112, 113 facing the moldingcavity 115). In another example, at least a portion of the mold parts112, 113 may be made of capacitor plates.

More generally, the mold parts 112, 113 may be comprised of a layeredconstruction. The mold part 112, 113 can, for example, each comprise alayered construction comprising a base plate, a molding plate definingat least part of the molding cavity 115, and an insulating layer on theinside of the molding plate (i.e. the side facing the cavity 115).Capacitor plates may also be included in such layered constructions.

The thickness of the molding plates and/or the capacitor plates may bevaried. For example, by varying the thickness of the molding platesand/or the capacitor plates, the mold parts 112, 113 may be contoured.This allows fine tuning of the energy that is to be applied to theparticles 120 in the mold 110. In some embodiments, adjusting thecapacitor plates might allow the same molding plates to be kept, whichmay be more economical than adjusting the molding plates themselves.

Further, a voltmeter may be used for measuring the voltage of thecapacitor. This may be helpful for determining the thermal outputintroduced into the particles 120 because the power is proportional tothe square of the voltage.

At least one of the mold parts 112, 113 can also be formed of orcomprise a composite material. The composite material may comprise amatrix material comprising a plastic material and bodies embeddedtherein, wherein the bodies comprise or are made of a material which hasa better heat conductivity than the plastic material they are embeddedin.

The embedded bodies may be particles or fibers, for example. The bodiesmay be completely embedded in the matrix material. If the bodies areparticles, for example spherical particles, they may have a maximum sizeof 3 mm, of 2 mm or even of 1 mm. If they are fibers, they may have amaximum length of 20 mm, of 10 mm or even of 5 mm.

The matrix material may be made of a plastic material that is notelectrically conductive, for example, an epoxy resin. The bodies may bedispersed within the matrix material such that at least most of them arenot in contact with each other. In such a situation the bodies may bemade of an electrically conductive material. As a specific example, themold parts 112, 113 may both comprise capacitor plates as mentionedabove and the mold parts may further comprise a composite material madeof an electrically non-conductive plastic matrix material withelectrically conductive fibers embedded therein in such a manner that atleast most of them are not in electric connection with each other. Inthis case, the fibers can beneficially be arranged parallel to andadjacent to the capacitor plates.

For example, the embedded bodies may comprise or be made of mineralsubstances such as silica sand, a ceramic material, aluminum oxide,aluminum nitride, glass granules, frit, silicon carbide and/or magnesiumoxide. The embedded bodies may also be glass fibers or carbon fibers.

Carbon fibers are generally electrically conductive, for which reasonthey are to be arranged parallel and adjacent to the capacitor plates ofthe mold parts 112, 113, if such capacitor plates are included.

Magnesium oxide has a high thermal capacity, such that the mold 110 withmold parts 112, 113 can rapidly absorb the heat introduced into theparticles 120 during welding, and the resultant particle foam componentcools down quickly.

Another option is that the composite material comprises materials whichdo not, or only to a limited degree, absorb RF radiation. Such acomposite material does not influence/absorb the RF radiation, or onlyto a minimal extent. On account of the embedded bodies having a goodthermal conductivity, however, the composite material can still rapidlydissipate heat present in the molding cavity 115, leading to a fastercool-down of the component after fusion.

A mold part 112, 113 comprising such a composite material may further beprovided on its inside, i.e. on the side facing the molding cavity 115,with a coating which absorbs RF radiation more strongly than thecomposite material. Because of this, upon application of electromagneticradiation in the area adjacent to the molding cavity 115 the mold part112, 113 is heated, so that the foam particles 120 in the molding cavity115 may be heated evenly. In particular, this coating can have similarelectrical loss factor as the foam particles 120 to be welded in themold 110. The coating may be a plastic coating, which may be made of orcomprise PET (polyethylene terephthaltate) PEEK (polyether ketone), POM(polyoxymethylene), polyimide or PMMA (polymethyl methacylate).

An insulating layer can also be arranged on the inside of the mold 110(i.e. facing towards the molding cavity 115). An insulating layer mayhelp to avoid heating of the mold wall if the material of the insulatinglayer is chosen such that it does not get heated up by theelectromagnetic radiation. In some examples, electrically insulatingcoatings may be made from a material which is essentially transparent toelectromagnetic radiation, in particular RF radiation, said materialbeing, for example, PTFE, PE, PEEK.

For example, the coating or insulating layer may be made from a materialhaving a moderate loss factor, such as, e.g., PET (polyethyleneterephthalate), PEEK (polyether ketone), POM (polyoxymethylene),polyimides and PMMA (polymethyl methacrylate). Polyoxymethylene has adielectric loss factor D of approximately 0.008, and polymethylmethacrylate has a dielectric loss factor D of approximately 0.02 for RFradiation. These coatings are thus essentially transparent to RFradiation, since they absorb only a small part of the electromagneticradiation and may, due to the relatively low loss factor, be formed witha certain thickness of, for example, at least 2 mm, in particular of atleast 2.5 mm or at least 5 mm. In some embodiments, the coating is notthicker than 20 mm, in particular not thicker than 15 mm, and, in otherembodiments, not thicker than 10 mm, so that the part of the energy ofthe electromagnetic radiation absorbed by the coating is small.

On the other hand, as already mentioned, the inside of the mold 110 mayalso be covered with a plastic material which, with the appliedelectromagnetic radiation, has a similar dielectric loss factor as theplastic material to be processed in the molding cavity 115 (e.g., thesame loss factor as the material of the particles 120), so as to achievea homogenous heating over the entire molding cavity 115 and in the edgeportions thereof, when applying the electromagnetic radiation.

It is emphasized that the application of an insulating layer or of aplastic material with a similar loss factor as the particles 120 isavailable also for a mold 110 and mold parts 112, 113 which do notcomprise a composite material as discussed above.

As another example, if it is deemed helpful to heat the mold surfaceenclosing the molding cavity 115, heating wires may be arranged adjacentto the surface of the mold enclosing the molding cavity 115. The heatingwires are connected to a power source by which a heating current may befed into the heating wires. Again, heating the walls/mold surfaceadjacent to the molding cavity 115 can help to achieve a better surfacefusion of the particles 120, in particular of the particles abutting thewalls of the mold 110.

The loading of the mold 110 with the first material comprising theparticles 120 of the expanded material may, for example, proceed via afeed line 118 that is connected via an inlet with the cavity 115 of themold 110. In some embodiments, the loading proceeds by a plurality offeed lines and inlets.

Alternatively, or in addition, the loading may also proceed by themovable mold parts 112, 113 of the mold 110 initially being moved apartfrom one another, such that at least one opening is created between themold parts 112, 113 through which the loading proceeds (this option isnot explicitly shown in the figures). After the loading of the mold 110is completed, the movable mold parts 112, 113 may be moved togetherand/or the inlet(s) may be closed, such that the cavity 115 forms aclosed molding chamber. The state wherein the mold parts 112, 113 aremoved apart for loading with the first material with the particles 120may be referred to as the loading state or “crack-gap state”, and a moldthat uses such loading may be referred to as a “crack-gap molding tool”.

The amount by which the mold 110 is opened in the loading state mayinfluence the available loading volume of the mold 110. The availableloading volume may, in turn, influence the amount of material that is“worked into” the cushioning element, and hence the mechanicalproperties of the cushioning element like, for example, density,stiffness and/or elasticity.

Using a crack-gap during loading may, for example, help increase thedensity in a region of the particle foam component to be manufactured inwhich otherwise the density would turn out too low. For example, in sucha region the mold may be opened to a larger amount and thus “overfilled”with particles, leading to a stronger compression of the particles uponclosing of the mold and hence an increased density in the moldedcomponent.

More generally, the distance between the mold parts in the crack-gapposition influences the available loading volume and hence the amount ofparticles that may be filled into the mold 110 in the loading state, andalso the amount of compression the particles experience upon closing ofthe mold 110 (assuming, for example, the available loading volume iscompletely used and the mold 110 is always closed to the same finalposition; otherwise the filling height and the specific configuration ofthe closed position of the mold 110 may also influence the amount ofcompression). A larger distance between the mold parts 112 and 113 inthe crack-gap position, i.e. a larger crack height, will allow moreparticles to be filled into the mold 110, which are therefore morestrongly compressed when the mold 110 is closed, compared to a smallercrack height (again assuming, for example, that the available loadingvolume is completely used and the closed position of the mold is thesame irrespective of the crack height; if this is not the case, thefilling height and details of the closed position of the mold may alsoinfluence the compression, as already mentioned).

To summarize, the mold 110 may have two mold parts 112 and 113 (or morethan two mold parts, but this is not discussed here explicitly, forconciseness) and in crack-gap molding the two mold parts 112, 113 arearranged in a crack-gap position in which they are spaced apart from oneanother a certain distance compared with the closed position for loadingof the mold 110, and they are subsequently pressed together beforefusion of the surfaces of the particles 120, thereby compressing theparticles within the molding cavity 115. The distance between the moldparts 112 and 113 during loading, i.e. the amount the mold 110 is openedfor loading, influences the available loading volume between the twomold parts 112 and 113, and it may hence influence or determine theamount of particles 120 that may be loaded into the mold 110. This, inturn, may influence or determine the amount of compression experiencedby the particles 120 upon closing of the mold 110.

During filling of the mold 110, the mold parts 112 and 113 may be spacedapart at varying distances in different areas of the mold 110, so thatduring closing of the mold 110, the mold parts 112 and 113 are movedtogether over different distances in the different areas. For example,the mold parts 112 and 113 may comprise several individual sub-parts andthe crack height between a sub-part on the first mold part 112 and acorresponding sub-part on the second mold part 113 may be individuallycontrolled and varied for each sub-part. In some embodiments, only oneof the two (or more) mold parts 112 or 113 comprises such individualsub-parts, while the other mold part(s) does not, which may allow for asimpler mold construction. With at least one mold part 112 or 113comprising individually controllable sub-parts, the crack height andhence the loading of the mold 110 and compression of the first materialwith the particles 120 may still be locally controlled.

Hence, the first material and, in particular, the foam particles 120 maybe compressed with differing strength in different areas of the mold110. Thus, in some embodiments, different densities in the closed stateof the mold 110 may be obtained. In other embodiments, variations indensity due to different thicknesses in the molding cavity 115 may belevelled out or compensated for.

If, for example, soles for footwear are produced in the mold 110, thenthe resulting particle foam component is generally much thinner in thefront section than in the rear. In cross-section, such a sole has aroughly wedge-shaped form. If one mold part 112 or 113 is, for example,pivoted around a swivel axis to create the crack-gap position, said axisbeing arranged transversely to the longitudinal axis of the mold 110 atthe thinner end of the mold 110 (in other words arranged eccentrically)then on swiveling back into the closed position of the mold 110 aroughly constant density of the foam particles 120 contained therein isobtained. This option may, therefore, be beneficially applied for themanufacture of products which are wedge-shaped in cross-section. Torepeat, during closing of the mold 110, the mold parts 112 and/or 113may, for example, be pivoted around an eccentrically arranged swivelaxis.

Moreover, individually controllable sub-parts for of the mold parts 112and/or 113, or an eccentrically arranged swivel axis or axes, may alsobe used to compress areas of the molding cavity 115 with differentthickness as evenly as possible, in order to obtain the most evenheating and quality of fusion in the whole particle foam component. Itmay, however, also be expedient, if certain areas are to be heated morestrongly, that greater compression take place in these areas so that, onaccount of their greater density, the foam particles 120 located thereinabsorb electromagnetic radiation more strongly. Consequently, duringproduction of the particle foam components, in some embodiments, apredetermined, non-constant temperature profile is set.

It is mentioned that within the scope of the present invention, theaspects concerning the crack-gap loading of the mold 110 described justnow may be practiced individually, without pre-heating of the particles120, but also in combination with the further aspects and features ofthe present invention described above and below.

FIG. 1b shows the closed mold 110 loaded with the first material withthe particles 120 of the expanded material. The at least one feed lines118 and/or inlets may be connected to the mold 110 or mold parts 112,113. For the processing, in some examples, at least one air channel maybe added. In this way, in some embodiments, air may be injected forcooling and/or stabilization. Also, in some embodiments, excess gas maybe diverted or the pressure reduced in the mold.

In some examples, the particles 120 may be swirled when they are loadedinto the mold 110. This may be achieved by air streams or anothergaseous stream. The air stream may be applied to the mold 110 by thefeed lines 118 or in the inlets also used for loading the particles 120,or specific lines may be used for injecting air streams into the mold110. Swirling may be desirable to separate the particles when loadingthem into the mold so as to avoid clustering thereof and to enabledistribution thereof.

As mentioned above, prior to being loaded into the mold 110, theparticles 120 may, for example, be stored in a storage container and/orbe intermixed, coated, soaked or impregnated with the energy absorbingmaterial, and so forth. As mentioned above, the energy absorbingmaterial may be added to the particles 120 in a feed line 118 which isused for loading the mold 110 with the particles 120. This may allow adosed addition of the energy absorbing material such that the amount ofenergy absorbing material per particle 120 may be adjusted and variedduring the loading of the mold 110. The use of an energy absorbingmaterial may be beneficial, for example, to permit a material to be ableto absorb RF energy, i.e. to make it RF active (or active with regard tosome other kind of electromagnetic radiation and/or induction. An energyabsorbing material can also be used to reduce the necessary energy bypre-heating rather than RF fusing. Also, when trying to balance the RFabsorption of multiple materials in one component, the use of an energyabsorbing material might help. Its use may, for example, help to achieveoperation within an ideal processing range, whereby one material has itsprocessing window (or both) adjusted so that an optimum window may befound.

The loading of the particles 120 in some examples may be achieved byrepeatedly opening and closing the material container. For example,opening and closing times may be on the order of 500 milliseconds to 1second. In this way, the particles may be conveyed intermittently fromthe container to the feed line 118 and eventually to the mold 110. Thismay lead to breaking up a bridging of the foam particles 120 so that theparticles 120 get at least partly isolated. This may be beneficial inthe case of foam particles 120 having an adhesive surface, such as,e.g., eTPU foam particles 120.

Once there is a sufficient amount of particles 120 in the mold 110, themold 110 is closed and/or the feed lines 118 and/or inlets are closed.In order to determine whether a sufficient amount of particles 120 hasbeen loaded, the mold 110 can, for example, be filled by volume and whena feedback pressure is high enough it is assumed that the mold 110 isfilled sufficiently. Or the mold 110 is filled based on weight.

In some examples, a variable pressure may be applied to the moldingcavity 115. The addition of pressure to the molding cavity 115 canenhance the processing of the particles 120. For example, when applyingpressure to the molding cavity 115 during loading, this also improvesthe ability to load the mold 110 as the particles 120 are made smaller,i.e. are under compression. Further, a negative pressure may be applied(i.e. a vacuum). This is beneficial if the foam particles 120 and/or thesupplied compressed air have a certain moisture.

The particles 120 may be randomly arranged. However, the particles 120or at least some of the particles 120 may also be aligned to each otheror be otherwise intentionally arranged within the mold 110.

The particles 120 may, for example, comprise at least one of thefollowing materials: expanded thermoplastic polyurethane (eTPU), forexample eTPU which has a dielectric loss factor D of 0.2 at anelectromagnetic radiation with a frequency of 1 MHz, expanded polyamide(ePA), and/or expanded polyether-block-amide (ePEBA). Other materialsthat may be used include PLA, PEBA, PET, PBT and TPEE. The firstmaterial may only comprise one kind of particles 120. In otherembodiments, the first material with which the mold 110 is loadedcomprises a mixture of different kinds of particles 120. For example,the particles 120 may differ in their material, shape, size, color,density, and/or combinations thereof, as well as their respectiveexpanded material. For instance, depending on the purpose of the plasticcomponent to be formed, the diameter of the particles 120 may, in someembodiments, be in the range of 3 mm to 5 mm.

In some embodiments, the particles 120 comprise an energy absorbingmaterial that absorbs the energy supplied by the at least oneelectromagnetic field—as already mentioned and as further describedbelow—and therefore contributes to the fusing (or the pre-heating) ofthe surfaces of the particles 120. This energy absorbing material may,for example, be added to the particles 120 prior to the loading of themold 110. For example, the particles 120 may be provided with the energyabsorbing material prior to loading of the mold 110 by storing them inthe material or intermixing them with the material. In some embodiments,the energy absorbing material is added to the particles 120 during theloading of the mold 110, as shown in FIG. 1a , for example by a hopper119 in the feed line 118.

In the simplest case, the particles 120 are provided with a constantamount of the energy absorbing material. That is, the amount of energyabsorbing material is essentially the same for all particles 120.Herein, “essentially the same” may mean: as far as the method used forthe addition of the energy absorbing material and the variation in thesize of the particles 120 allows. Hence, in this case, there may be anessentially homogeneous distribution of the energy absorbing materialwithin the first material with the particles 120.

In some embodiments, the added amount of energy absorbing material perparticle 120 varies within the mold 110. This may, for example, beachieved in that, prior to the loading of the mold 110, mixtures ofparticles 120 and energy absorbing material are prepared which eachcomprise a different content of energy absorbing material, and with whomthe mold 110 is subsequently loaded according to the desireddistribution of the energy absorbing material within the mold 110. Or,the amount of energy absorbing material added through the hopper 119 isvaried accordingly during the loading of the mold 110.

By a varying amount of energy absorbing material, the amount of energysupplied to the particles 120 by the electromagnetic field (the step ofsupplying energy in the form of at least one electromagnetic field willbe further discussed below), i.e. the amount actually absorbed by theparticles, may be locally influenced. For example, the amount of energyabsorbed by the particles from the electromagnetic field may beproportional to the amount of energy absorbing material a given particle120 comprises. The amount of energy a particle 120 absorbs may in turnhave an influence on how strongly the surface of the particle 120 isfused with the surfaces of its neighboring particles. For example, thesurface of the particle 120 is fused together with the surfaces of theneighboring particles the stronger, the more energy is supplied to andabsorbed by the particle 120.

For example, FIG. 1c illustrates the case in which the mold 110 isloaded with three layers 122, 123 and 124 of particles 120, wherein thethree layers 122, 123 and 124 each comprise a different amount of energyabsorbing material per particle 120. In the case shown here, the bottomlayer 122 comprises the largest amount of energy absorbing material perparticle 120 and the top layer 124 the smallest amount. As alreadymentioned, the amount of energy absorbing material per particle 120 mayalso vary in a different manner within the mold 110, in order to adjustthe desired degree of the fusing of the surfaces of the respectiveparticles 120 locally.

The energy absorbing material may, for example, comprise water or becomprised of water, or it may be comprised of a material which comprisesa metal, for example a metal powder like iron filings. The choice of theenergy absorbing material may depend on the way in which the energy thatleads to the fusing of the surfaces of the particles 120 is supplied.

Speaking of which, the method 100 may further comprise the fusing of thesurfaces of the particles 120 by supplying energy, wherein the energy issupplied in the form of at least one electromagnetic field 130, 140. Thecycle time for a fusing step depends on various parameters (for example,the density of the particles 120) and may be optimized to be within adesired range. A benefit of the process is that the fusing step may bemade very short, for example, the cycle time for a fusing step may be inthe range from 5 seconds to 2 minutes. This means that, compared toconventional steam molding of eTPU/particle foams for, e.g., sportinggoods, the cycle times may be significantly shorter.

It is to be noted that the method of manufacturing may also involvemeasuring a state of the mold 110, as well as the various components. Inparticular, a temperature of the particles 120 in one or several placeswithin the mold 110 may be measured. This is beneficial to optimize thecycle time and to adjust the parameters (such as electromagneticradiation) to obtain a reliable fusing of the particles 120.

The energy may, for example, be supplied in the form of electromagneticradiation 130, as shown in FIG. 1d . Herein, the radiation 130 may beemitted from a radiation source 131.

The radiation 130 may, for example, be radiation 130 in the microwaverange, i.e. radiation with a frequency in the range from 300 MHz to 300GHz. The radiation 130 may also be radiation in the radiofrequencyrange, i.e. radiation with a frequency in the range from 30 kHz to 300MHz.

In some embodiments, the energy is supplied in the form of radiation 130in a frequency range different from the frequency ranges just mentioned.As a specific example, the energy may be supplied in the form ofinfrared (IR) radiation 130. The use of ultraviolet (UV) radiation 130may also be considered.

If the radiation 130 is radiation in the microwave range, water may bewell suited as an energy absorbing material, because irradiating waterwith microwave radiation leads to a heating up of the water. Also forradiation 130 in the radiofrequency range or infrared range, water maybe considered as energy absorbing material.

As shown in FIG. 1e , the energy may further be supplied byelectromagnetic induction. To this end, an induction generator 141 (andin some embodiments, multiple induction generators) generates anelectromagnetic field 140 which comprises a magnetic flux Φ that variesover time. When using electromagnetic induction, the particles 120, insome embodiments, comprise an energy absorbing material that possesses acertain electric conductivity, for example a metal powder like ironfilings. Then, the time varying magnetic flux Φ can create eddy currentsin this electrically conducting material which heat up the material andhence contribute to the fusing of the surfaces of the particles 120.

In the embodiments shown in FIGS. 1d and 1e , all partial regions of themold 110 are provided with approximately the same amount of energy inthe form of the electromagnetic fields 130, 140. It must be kept inmind, however, that the amount of energy that is supplied to theparticles 120 for the fusing of the surfaces, i.e. the amount of energythat is actually absorbed by them, does not only depend on the amount ofenergy that is made available by the electromagnetic fields 130, 140 inthe first place, but also on the percentage of the available energy thatthe particles 120 actually extract from the electromagnetic fields 130,140. As already explained above, this may be controlled by providing theparticles 120 with an energy absorbing material or by varying its dosagein different partial regions of the mold 110, for example.

As a further option, the mold 110 or mold parts 112, 113 may beselectively provided on their inside (i.e. the side facing the moldingcavity 115) with areas that absorb electromagnetic radiation morestrongly such that, when the electromagnetic radiation is applied, theareas absorbing the radiation more strongly heat up in such a way thatin this area the particles 120, and hence the surface of a particle foamcomponent, are more strongly melted than in the remaining areas. Theseareas which absorb electromagnetic radiation more strongly may beprovided with the shape of a specific mark, logo or the like, so thatthis shape is formed in the finished particle foam component by meltingthe surface of the particle foam component. In this way a marking may beprovided on the particle foam component, without the need for a separateprocessing step.

Alternatively or in addition, in some embodiments, the amount of energysupplied to the particles 120 is influenced by varying the amount ofenergy that is made available by the electromagnetic fields for thedifferent partial regions of the mold in the first place.

For example, FIGS. 1f and 1g show embodiments wherein more energy ismade available in a first partial region 150 of the mold 110 than in asecond partial region 155. This is achieved in that the first partialregion 150 is irradiated with electromagnetic radiation 130 with afrequency f1 and the second partial region 155 is irradiated withelectromagnetic radiation 135 with a frequency f2, wherein the frequencyf1 is higher than the frequency f2. Both frequencies f1 and f2 may, forexample, be chosen from the above mentioned frequency ranges(microwaves, radio waves, infrared, UV) or from at least one differentfrequency ranges. As a result, the radiation 130 “transports” moreenergy into the first partial region 150 of the mold 110 than theradiation 135 transports into the second partial region 155 of the mold110. As shown in FIG. 1f , in some embodiments, both kinds of radiation130 and 135 are emitted from a single radiation source 131. To this end,the radiation source 131 may, for example, comprise a device fordoubling the frequency. In some embodiments, however, as shown in FIG.1g , each of the two kinds of radiation 130 and 135 is emitted from arespective separate radiation source 131 and 136. The radiation may begenerated by a suitable radiation source comprising a circuit forguiding the electromagnetic waves. If the resonance frequency is used,the maximum power may be transferred.

Influencing the available amount of energy by a variation of thefrequency is, however, not the only option. FIG. 1h , for example, showsembodiments wherein the amount of energy made available for the partialregions 150 and 155 of the mold 110 is controlled via the intensity ofthe radiation 130 and 135 incident in these regions. Here, intensitydesignates the incident amount of energy per unit area and unit time ofthe electromagnetic radiation. In general, it is proportional to thesquare of the amplitude of the incident radiation.

As mentioned previously, in some embodiments, the particles 120 may bepre-heated prior to the actual fusing of the particles 120. In this way,the particles 120 may be heated to a specific temperature first so thatthey are, in some embodiments, in a designated absorption range withrespect to the electromagnetic radiation that is subsequently appliedfor the fusing. This pre-heating can take place in the mold 110 orbefore or during loading of the particles into the mold 110.

Similar to the use of an energy absorbing material described above,pre-heating the particles can, for example, be used when trying tobalance the RF absorption of multiple materials in one component, as itmight help to achieve operation within an ideal processing range,whereby at least one material has its processing window adjusted so thatan optimum processing window for the whole process may be found.

Pre-heating the particles 120 may be beneficial if it is done alreadyduring the loading step, but also while the mold 110 is being closed.Such pre-heating can increase the throughput of the system because thetime that is required for the actual fusing step, and therefore the timeneeded for keeping the particles 120 in the mold 110, may be reduced.

Additionally or alternatively, in some examples, RF radiation may beapplied at a first, lower, electric power or electric voltage (e.g.,during loading and/or when the particles 120 are in the mold 110) inorder to pre-heat the material to a specific temperature. Thereafter,the electric power or electric voltage may be increased, eithergradually or abruptly. The electric power or electric voltage may beapplied at lower values before it gets increased at different partialregions (e.g., regions 150, 155) of the mold 110. Thus, only a partialpre-heating of the particles 120 may be obtained. This may be helpfulwhen using particles 120 having different properties (e.g., size orabsorbing material).

The electric power or electric voltage of the electromagnetic radiation130, 135, 140 may also be increased gradually. For example, a ramp up ofthe radiation power may be chosen such that the complete cycle time forthe production of a single component lies within a desired range forproduction. For example, in the range of 5 sec-2 min. Compared toconventional methods for the manufacture of sporting goods, theinventive method can thus be significantly faster. In general, ramp uptime of the radiation power may be chosen quite freely and it may beadjusted in order to control the fusion process of the surfaces of theparticles 120 and, thus, the overall fusion of the component. Forexample, depending on material of the particles 120, too fast a ramp upmight damage the cell structure of the particles. While too slow a rampup may be inefficient or lead to subpar fusion results.

After the pre-heating, the electromagnetic radiation 130, 135, 140 maybe applied to achieve an optimum transfer of power. This approach mayalso be helpful if materials are used which comprise a temperaturedependent dielectric loss factor.

While in the embodiments shown in FIG. 1h both kinds of radiation 130and 135 have the same frequency f1 and the radiation 130 has theintensity I1 that is higher than the intensity I2 of the radiation 135,it is clear to the skilled person that, in other embodiments, avariation of the intensity may be combined with a variation of thefrequency, and that generally more than two different kinds of radiationmay be used.

Reference is further made to the fact that also for the creation of twoor more radiations 130, 135 with different intensities, a singleradiation source may be used. However, in FIG. 1h the radiation 130 withthe higher intensity I1 is emitted by the radiation source 131 and theradiation 135 with the lower intensity I2 is emitted from the separateradiation source 136.

In addition, in the embodiments shown in FIGS. 1f-h , the firstradiation 130 only irradiates the first partial region 150 and thesecond radiation 135 only the second partial region 155. However, indifferent embodiments (not shown), a first electromagnetic field, forexample the electromagnetic field 135 from the source 136, provides theentire mold 110 with a basic amount of energy as a base field and anincrease in the energy made available in one partial region of the mold110, e.g. an increase of the energy made available in the partial region150, is achieved by irradiating this partial region with radiation froman additional radiation source, e.g. with the radiation 130 from thesource 131. In other words, individual partial regions of the mold 110may be provided with additional energy by additional electromagneticfields, e.g. in the form of radiation or electromagnetic induction.

Reference is again made to the fact that the amount of energy actuallysupplied to and absorbed by the particles 120 in general also depends onfurther factors, in particular the amount of potentially added energyabsorbing material and the absorbing power of the expanded material ofthe particles 120 itself.

It is again highlighted that a benefit of the present method 100 may bethat the mold 110 only absorbs a limited amount of energy compared tothe first material with the particles 120. For example, the use of epoxyresin for the manufacture of molds 110 has turned out beneficial. Epoxyresin may be processed to molds 110 with complexly shaped cavities 115and it can comprise a low absorption power with respect toelectromagnetic fields. Other methods known in the art for themanufacture of a mold with low absorption capabilities may also be used.

A ratio of the amount of energy absorbed by the first material with theparticles 120 divided by the total amount of energy which is absorbed byfirst material and the mold 110 may lie in the range 1.0-0.2, or in therange 1.0-0.5, or even better in the range 1.0-0.8. The exact value ofthis ratio will, in general, depend on a plurality of factors like, forexample, the material used for the manufacture of the mold 110, itsmass, and the kind of electromagnetic field(s) used. The higher thisratio is, the higher the amount of energy that is utilized for fusingthe particle 120 and the lower the amount of energy that is “lost” inthe mold 110.

Further embodiments are shown in FIG. 1i , wherein the mold 110 wasfurther loaded with a second material 160 which remains essentiallyunaltered by the used electromagnetic field 140. “Essentially unaltered”may mean that the amount of energy absorbed by the second material 160is not enough to melt or start melting the second material 160 or tosoften or harden it.

While in the embodiments shown in FIG. 1i the energy is supplied viaelectromagnetic induction 140, reference is made to the fact that thefollowing explanations also apply when supplying the energy by adifferent electromagnetic field, for example via electromagneticradiation like the radiations 130 or 135. For reasons of conciseness,reference is made to the electromagnetic field 140 in the following.

The second material 160 may, for example, in itself comprise a lowabsorption power with regard to the used electromagnetic field 140. Inparticular, the second material 160 may be free from energy absorbingmaterial or comprise a lower content of energy absorbing material thanthe first material with the particles 120. The second material 160 may,for example, also comprise particles of an expanded material like eTPU,ePA and/or ePEBA, but without or with less energy absorbing material.

The particles of the second material may be randomly arranged. Or, theparticles or at least some of the particles of the second material maybe aligned to each other or be otherwise intentionally arranged withinthe mold 110.

The second material 160 may also comprise a different foamed orun-foamed plastic material. The second material 160 may, for example,comprise foamed ethylene-vinyl-acetate (EVA).

Optionally, the mold may also be loaded with further materials, inparticular with further materials which also remain essentiallyunaltered by the electromagnetic field 140. For example, in theembodiments shown in FIG. 1i , the mold 110 was loaded with a thirdmaterial 165 which remains essentially unaltered by the electromagneticfield 140. The third material 165 may, for example, be rubber. Withregard to such further materials, the considerations made with respectto the second material 160 analogously apply.

In the embodiments shown in FIG. 1i , the first material with theparticles 120, the second material 160, and third material 165 arearranged in a layered manner. The skilled person will understand,however, that the first material, the second material 160, and potentialfurther materials may also be arranged in a multitude of differentarrangements within the mold 110. Hence, the inventive method 100 allowsthe manufacture of many differently shaped plastic components.

The shape of the mold 110 and the positioning of the first material withthe particles 120 as an intermediate layer between a top layer with thesecond material 160 (for example foamed EVA) and a bottom layer with thethird material 165 (for example rubber) as shown in FIG. 1i may be wellsuited for the manufacture of a cushioning element for sports apparel,e.g. a shoe sole or a part thereof. A shoe sole manufactured in this waymay then be further processed to a shoe, for example a sports shoe.

Further, the manufacturing method 100 may also involve a step ofstabilizing the particle foam component after fusing. This may be doneby keeping the component in the mold 110/tool after fusing so that thecomponent maintains the desired part shape. In some examples, thecomponent can also be actively cooled to accelerate the stabilization ofthe component. Active cooling may involve supplying ambient air or somegaseous or liquid coolant. The mold 110 may also comprise coolingchannels or cooling ribs for this purpose.

The method 100 may also comprise the step of demolding the component, astep which may be carried out in a separate demolding station. In someexamples, the demolding may be carried out by taking the molding parts112, 113 apart from each other. Also, demolding tappets may be providedfor demolding, by which the component is pushed out of one of the twomolding parts 112 and 113.

Finally, reference is again made to the fact that when performing themethod 100, the options and design selections discussed herein may becombined with one another arbitrarily, and the embodiments explicitlydiscussed herein only provide some specific examples to facilitate theunderstanding of the invention. The inventive method 100 may, however,not be limited to the embodiments explicitly described herein.

FIGS. 2a-c show exemplary plastic components 201-203 that may bemanufactured according to the methods described herein. Therein, plasticcomponent 201 comprises particles of ePEBA, whereas plastic components202-203 each comprise particles of eTPU.

It is noted that some edges of the plastic components 201-203 as shownin FIGS. 2a-c have been cut such that not all edges have a surfacestructure as created by fusing the plastic components in a mold.

Embodiments of an apparatus 1 for the manufacture of particle foamcomponents is now explained below with the aid of FIG. 3. This apparatus1 has several workstations, spatially separate from one another andconnected to one another by a conveyor unit 60. With the conveyor unit60, several molding tools 3, each defining a molding cavity, may bemoved between the individual workstations.

The conveyor unit 60 has an upper conveyor section 61 and a lowerconveyor section 62, on which the molding tools 3 are conveyed indifferent directions. The two conveyor sections 61, 62 are arrangedparallel to one another, and at the ends of the two conveyor sectionthere is in each case a lifting device 63, 64 by which the molding tools3 may be moved downwards (lifting device 63) or upwards (lifting device64) between the conveyor levels. The two conveyor sections 61, 62 eachhave two narrow conveyor belts, arranged parallel to one another and onwhich the molding tools 3 may be placed.

Located on the upper conveyor section 61 are, in the direction ofconveyance, a demolding station 66, an insertion station 67, a fillingstation 68 and a welding station 69. The welding station 69 includes apress with a stationary bottom plate, at the level of the upper conveyorsection 61, and a movable top plate. Between the two plates (notdepicted), in each case a molding tool 3 may be arranged and, by apress, the two plates are actuated, i.e. pressed together. The twoplates are made of an electrically conductive material. The bottom,stationary plate is connected to the ground. The top, movable plate isconnected to an RF generator 19. The two plates thus form capacitorplates which accommodate the molding tool 3 between them.

Provided on the lower conveyor section 62 is a cooling section 70, onwhich the molding tools 3 heated at the welding station 69, and theparticle foam components located therein, may cool down. The coolingsection 70 is able to cool the molding tools 3 with ambient air alone,but may be provided with a fan, in order to subject the molding tools 3to a cooling airflow and/or may include a cooling chamber which iscooled below room temperature by a cooled medium, in order to acceleratethe heat-transfer out of the molding tool 3. The cooling section 70 mayhold several molding tools 3 simultaneously, since the cooling and/orstabilizing of the particle foam component in the molding tool 3 is theworking step of longest duration.

Provided on the lower conveyor section 62 is a molding tool storagesystem 71 which is connected to an automatic store for the storage ofseveral molding tools 3, so that different molding tools 3 may be fedinto and taken out of the conveyor unit 60 automatically.

The manufacture of a particle foam component finishes in the demoldingstation 66, in which the molding tool 3 comprised of two halves isopened and the particle foam component produced therein is removed anddischarged.

The molding tools 3 have a closing mechanism 72, by which the two halvesof the respective molding tool 3 are firmly closed together whenconveyed along the conveyor unit 60. This closing mechanism 72 is openedautomatically in the demolding station 66 for demolding of the particlefoam component, after which the two mold halves are put together againand joined together by the closing mechanism 72. The closing mechanism72 joins the two mold halves so firmly that they do not move apartduring conveyance. The closing mechanism 72 may have a degree of play,so that the two mold halves may be pulled slightly apart during filling,in order to form a crack-gap. The closing mechanism 72 must not be usedto absorb the pressure occurring in the molding cavity during welding.This pressure is drawn off via the press in the welding station 69.

The benefit of this apparatus 1 is that a very high throughput ispossible with a single welding station 69, since the welding of aparticle foam component generally lasts no longer than 30 seconds to 2minutes. The working step of longest duration is the stabilizing orcooling down of the molding tool 3 and the particle foam componentcontained within it. Since the cooling section 70 is able to holdseveral molding tools 3 simultaneously, several molding tools 3 may bestabilized or cooled at the same time. This means that the processing ofthe molding tools 3 into the welding station 69 is not delayed.

A further benefit of this apparatus 1 lies in the fact that differentmolding tools 3, in particular with different molding cavities, may becirculated simultaneously. In some embodiments, each molding tool 3 isprovided with a unique machine-readable identification device. Such anidentification device may be for example a barcode or an RFID chip. Atleast one suitable readers for reading the identification device areprovided on the apparatus 1 along the conveyor unit 60, so that acontrol unit (not depicted) knows which molding tool 3 is present atwhich workstation. By this, the molding tools 3 may be dealt withindividually. In particular, at the welding station 69, they may besubjected to electromagnetic waves of different voltage and/or duration.The dwell time in the cooling section and the cooling effect underactive cooling, for example using a fan, may be individually controlled.

In comparison with a conventional apparatus for the manufacture ofparticle foam components, in which the foam particles are welded solelywith hot steam, the present apparatus 1 is much more compact and muchmore flexible, since it is able to process several different moldingtools 3 simultaneously. Moreover, energy may be introduced into themolding cavity with much greater efficiency by the electromagneticradiation.

It may also be expedient to provide at the welding station 69 a water orsteam supply line, by which water and/or steam may be fed to the moldingtool 3. This is especially desirable when the foam particles to bewelded have, at low temperatures or generally, only a low dielectricloss factor. In such a case, a limited amount of water or steam issupplied. By the electromagnetic radiation, the water is heated tosteam, or the steam is heated further. In this way, the foam particlesare heated to a higher temperature at which the dielectric loss factoris greater, so that the electromagnetic radiation is absorbed and theyare heated further. It has been found that just a few hundred grams ofwater are sufficient for a molding cavity with a volume of 50 liters. Ifthe foam particle material is, for example, ePS (expandable polystyrol),then 300 g of water or less are sufficient for heating and welding thefoam particles in a molding cavity with a volume of 50 liters. Inconventional welding, in which the foam particles are heated solely byhot steam, amounts of steam comprising several kilos of water are neededfor a molding cavity with a volume of 50 liters.

It therefore applies, in principle, if foam particles are to be weldedwhich absorb electromagnetic radiation to only a limited extent, that asingle addition of water amounting to 300 g is sufficient for a moldingcavity with a volume of 50 liters. For many materials which absorbelectromagnetic radiation only slightly, even small amounts of water maybe adequate. For molding cavities with different volumes, the maximumamount of water required may be matched to the volume in the sameproportion.

If water is heated in the molding cavity using electromagneticradiation, then it is expedient to use a molding tool 3 which has apressure sensor, by which the pressure prevailing in the molding cavitymay be measured. This pressure is proportional to temperature. Theirradiation of electromagnetic radiation is then controlled, in someembodiments, in accordance with the measured pressure value, i.e. setfor a specific pressure value.

For this apparatus 1 with the conveyor unit 60, the different aspects ofthe invention described above and in particular the different moldingtools and embodiments of the method 100 may be used individually or incombination.

In the following, further embodiments are provided to facilitate theunderstanding of the invention:

1. Method for the manufacture of a plastic component, in particular acushioning element for sports apparel, comprising:

a. loading a mold with a first material which comprises particles of anexpanded material; and

b. fusing the surfaces of the particles by supplying energy,

c. wherein the energy is supplied in the form of at least oneelectromagnetic field.

2. Method according to the preceding embodiment 1, wherein the particlescomprise one or more of the following materials: expanded thermoplasticpolyurethane, eTPU; expanded polyamide, ePA; expandedpolyetherblockamide; ePEBA.

3. Method according to any one of the preceding embodiments 1-2, whereinthe particles further comprise an energy absorbing material, whichabsorbs the energy supplied by the at least one electromagnetic fieldsuch that the energy absorbing material contributes to the fusing of thesurfaces of the particles.

4. Method according to the preceding embodiment 3, wherein the particlesare provided with the energy absorbing material prior to the loading ofthe mold.

5. Method according to any one of the preceding embodiments 3-4, whereinthe energy absorbing material comprises water.

6. Method according to any one of the preceding embodiments 3-5, whereinthe energy absorbing material comprises a metal.

7. Method according to any one of the preceding embodiments 1-6, whereinthe energy is supplied in the form of radiation in the microwave range,300 MHz-300 GHz.

8. Method according to any one of the preceding embodiments 1-7, whereinthe energy is supplied in the form of radiation in the radio frequencyrange, 30 kHz-300 MHz.

9. Method according to any one of the preceding embodiments 1-8, whereinthe energy is supplied by electromagnetic induction.

10. Method according to any one of the preceding embodiments 1-9,wherein more energy is supplied to the particles in a first partialregion of the mold than in a second partial region of the mold.

11. Method according to any one of the preceding embodiments 1-10,wherein energy is supplied to the particles in a first partial region ofthe mold with an electromagnetic field with a first frequency (f1) andin a second partial region of the mold with an electromagnetic fieldwith a second frequency (f2), wherein the second frequency (f2) isdifferent from the first frequency (f1).

12. Method according to any one of the preceding embodiments 3-11,wherein the average amount of energy absorbing material per particlevaries within the mold.

13. Method according to any one of the preceding embodiments 1-12,wherein the mold is further loaded with a second material, which remainsessentially unaltered by the at least one electromagnetic field.

14. Method according to the preceding embodiment 13, wherein the secondmaterial also comprises particles of an expanded material, in particularparticles of eTPU, ePA, and/or ePEBA.

15. Method according to any one of the preceding embodiments 1-14,wherein a ratio of the amount of energy absorbed by the first materialto the total amount of energy absorbed by the first material and themold lies in the range 1.0-0.2, preferably in the range 1.0-0.5, andparticularly preferably in the range 1.0-0.8.

16. Method according to any one of the preceding embodiments 1-15,wherein the mold comprises an epoxy resin.

17. Plastic component, in particular cushioning element for sportsapparel, manufactured with a method according to any one of thepreceding embodiments 1-16.

18. Shoe, in particular sports shoe, with a cushioning element accordingto embodiment 17.

19. Shoe according to embodiment 18, wherein the shoe is a running shoe.

Different arrangements of the components depicted in the drawings ordescribed above, as well as components and steps not shown or describedare possible. Similarly, some features and sub-combinations are usefuland may be employed without reference to other features andsub-combinations. Embodiments of the invention have been described forillustrative and not restrictive purposes, and alternative embodimentswill become apparent to readers of this patent. Accordingly, the presentinvention is not limited to the embodiments described above or depictedin the drawings, and various embodiments and modifications may be madewithout departing from the scope of the claims below.

That which is claimed is:
 1. A method for manufacturing a plasticcomponent, in particular a cushioning element for sports apparel,comprising: loading a mold with a first material, which comprisesparticles of an expanded material; and while loading the mold,pre-heating the particles by supplying energy, wherein the energy issupplied in a form of at least one electromagnetic field.
 2. The methodaccording to claim 1, wherein the loading step comprises transportingthe particles from a container to the mold via at least one feed line.3. The method according to claim 2, wherein the particles are pre-heatedwhile in at least one of the container and the at least one feed line.4. The method according to claim 1, wherein the particles are pre-heatedin the mold prior to closing the mold.
 5. The method according to claim1, wherein the energy supplied by the at least one electromagnetic fieldis varied over time.
 6. The method according to claim 1, wherein theenergy supplied by the at least one electromagnetic field is graduallyincreased over time.
 7. The method according to claim 1, furthercomprising a step of fusing surfaces of the particles by supplyingenergy in a form of at least one electromagnetic field.
 8. The methodaccording to claim 7, wherein the form of the at least oneelectromagnetic field used for pre-heating the particles is differentthan the form of the at least one electromagnetic field used for fusingthe surfaces of the particles.
 9. The method according to claim 1,wherein the particles comprise at least one of: expanded thermoplasticpolyurethane, eTPU; expanded polyamide, ePA; expandedpolyetherblockamide, ePEBA; polylactide, PLA; polyether-block-amide,PEBA; polyethylene terephthalate, PET; polybutylene terephthalate, PBT;and thermoplastic polyester ether elastomer, TPEE.
 10. The methodaccording to claim 7, wherein the particles further comprise an energyabsorbing material, which absorbs the energy supplied by the at leastone electromagnetic field such that the energy absorbing materialcontributes to the step of fusing the surfaces of the particles.
 11. Themethod according to claim 10, wherein the particles are mixed with theenergy absorbing material prior to the loading step.
 12. The methodaccording to claim 10, wherein the energy absorbing material comprisesat least one of water and a metal.
 13. The method according to claim 1,wherein the energy is supplied in a form of radiation in a microwaverange, 300 MHz-300 GHz.
 14. The method according to claim 1, wherein theenergy is supplied by electromagnetic induction.
 15. The methodaccording to claim 7, wherein more energy is supplied to the particlesin a first partial region of the mold than in a second partial region ofthe mold.
 16. The method according to claim 7, wherein the energy issupplied to the particles in a first partial region of the mold with anelectromagnetic field with a first frequency and in a second partialregion of the mold with an electromagnetic field with a secondfrequency, wherein the second frequency is different from the firstfrequency.
 17. The method according to claim 10, wherein an averageamount of the energy absorbing material per particle varies within themold.
 18. The method according to claim 1, wherein the mold is furtherloaded with a second material, which remains substantially unaltered bythe at least one electromagnetic field.
 19. The method according toclaim 7, wherein a ratio of an amount of energy absorbed by the firstmaterial to a total amount of energy absorbed by the first material andthe mold lies in a range of 1.0-0.2.
 20. A method for manufacturing acushioning element for sports apparel, comprising: opening a mold by apredetermined amount into a loading position, wherein the mold comprisesat least two mold parts and the predetermined amount by which the moldis opened influences an available loading volume of the mold; loading afirst material which comprises particles of an expanded material intothe loading volume created by opening the mold; closing the mold into aclosed position; and fusing surfaces of the particles by at leastsupplying energy in a form of at least one electromagnetic field. 21.The method according to claim 20, wherein in the loading position of themold, the at least two mold parts are in different areas of the moldspaced apart at varying distances compared to the closed position of themold, so that during the step of closing the mold, the at least two moldparts are moved together over different distances in the differentareas.
 22. The method according to claim 21, wherein at least one of theat least two mold parts comprises several individual sub-parts, andwherein a distance between the at least two mold parts in the loadingposition of the mold may be individually controlled for each sub-part inorder to obtain the varying distances in the different areas.
 23. Themethod according to claim 21, wherein during the step of closing themold, at least one of the at least two mold parts is pivoted around aneccentrically arranged swivel axis.
 24. The method according to claim21, wherein during the step of closing the mold, the particles aredifferently compressed in the different areas of the mold.
 25. Themethod according to claim 21, wherein the predetermined amount by whichthe mold is opened influences mechanical properties of the cushioningelement.
 26. The method according to claim 21, wherein the cushioningelement is a shoe sole or part of a shoe sole.